Such a valve typically has a housing with at least one inlet port and at least one outlet port for the liquid as well as an interposed connector fitting with a controller, a first flow regulator, and a second flow regulator therein. The connector fitting or parts thereon have connection formations for an adjuster acting on the first flow regulator on the one hand and connection formations for an actuator acting on the manually operable second flow regulator on the other hand, and the controller maintains the differential pressure constant via the first flow regulator and the second flow regulator.
Such a control valve is known, for example, from EP 2 271 969 [U.S. Pat. No. 8,763,632]. In the known control valve, the structural solution provided is such that, in the flow direction of the liquid in a cartridge-like unit from the inlet port, the controller is first installed with a sleeve-shaped flow restriction and subsequently with a flow cross section on which an actuator can act, and then a flow device that can be adjusted by manual actuation.
In such valve combinations, even when an actuator is installed, the flow cross section associated therewith can be adjusted by a handle not concealed by the actuator. This is a crucial advantage.
This advantage is to be maintained with this invention. In the solution according to the prior art, the entire throughput of liquid must first flow through the controller, which necessitates a large-diameter flow passage through the sleeve-shaped flow restriction of the controller. The sleeve-shaped flow restriction is enclosed at one end by a diaphragm that is fixed in portions of the cartridge-like unit. The pressure control of the flow restriction is effected by the diaphragm. In this structural solution, the operative surface, which is determined substantially by the diaphragm diameter and the inside diameter of the sleeve-shaped flow restriction and on which the pressure upstream of and downstream of the two flow regulators can act, is reduced. This surface could only be enlarged if the outside diameter of the valve body were increased substantially.
The operative surface of the valve combination is also limited by the fact that the controller is integrated into the actuating spindle so as to be rotatable relative to the housing together with the valve body and valve seat, which requires at least one additional part between the outer periphery of the diaphragm and the inner wall of the housing. This additional part is practically formed by a wall of an insert in the valve body that receives the controlling parts.